* test case for insertBefore for jsx
* fix unshiftContainer and insertBefore
* use path.scope.push
* add test making sure computedKeys var declaration at the right block
* add comment
* nit [skip ci]
* Make @babel/plugin-class-features a normal helper package
This effectively disallows using it directly.
* Rename helper
* Style
* Don't add prefix to plugin name
* Move private methods plugin